The thermal building insulation don’t works with air leaks in the envelope
In the lower part of a building, by the natural range of pressures, prevail the air infiltrations that provide cool air (in the winter) and cool the heated inside.
On top predominate the air exfiltration, through which the warm air escapes outside.
This both represents a great energy inefficiency to be considered in any study or audit to achieve effective performance.
It is estimated that nearly half of the energy losses of housing type corresponds to uncontrolled air .
We are talking about two concepts: ventilation and airtightness. Ventilation is the air controlled entry: if you know this flow , therefore it is possible to know the energy costs involved. An efficient building must be tightness to have no uncontrolled air intakes. This air volume would be unknown and their energy costs as well.
The blower-door test measured and locate the air leaks of the building and it allows to know the volume of unwanted infiltrates according to EN 13829. The blower-door method was established in Sweden in 1975 and is fully consolidated in Europe and the U.S. as a basic test of tightness in buildings. It is one of the basics requirements in the Passivehaus standard.
It is based on generating a depression in the building with the normal air intakes sealed (vents, exhaust fans, …), using a calibrated fan. Measuring airflow and creates a graph relating to the pressure flow, to determine the number of air changes hour due to air infiltration.